In radio communications systems, messages (for example, voice, picture information or other data) are transmitted via electromagnetic waves. The electromagnetic waves are transmitted via antennas, with the carrier frequencies being in the frequency band intended for the respective system.
In addition to the requirement to restrict the dimensions of the antenna for mobile radio transmitting and receiving devices, there is also an increasing requirement for the capability to transmit and receive in different frequency bands. For this reason, antennas are required which can be used in a number of frequency bands.
When using conventional antennas (for example, rod antennas as are used, in particular, in mobile parts) the required coverage of a frequency band which is as wide as possible, or of a number of frequency bands, cannot be ensured since the impedance and antenna gain of the antenna vary severely as a function of the frequency. As such, it is impossible to use the antenna in certain frequency ranges.
Thus, in order to solve this problem, antenna systems have been used which include a number of antennas, each of which covers a specific frequency range.
Antenna systems such as these have the disadvantages that they require more space and, moreover, the matching of the antennas to the individual frequencies from the respective frequency band is less than optimum.
An object to which the present invention is directed to design a mobile radio transmitting and receiving device such that, while covering a wide frequency range, it ensures a virtually constant, stable antenna gain.
Accordingly, the mobile radio transmitting and receiving device of the present invention has an electrically effective antenna body, in whose near field a dielectric body is mounted such that it can move. As such, the dielectric body can be moved in the near field of the antenna body such that the extent to which the dielectric body and the electrically effective antenna body overlap in the near field is varied. The resonant frequency which can be set, in this case, becomes lower the greater the extent of the overlap in the near field of the antenna body. In order to make it possible to adjust the extent of the overlap, it is possible to adjust the position of the dielectric body. The position is varied on the basis of at least one control signal, which is produced as an output signal by a control device and is passed to an adjusting part of the device. The control signal is produced by the control device until the extent of the overlap ensures an optimum value of at least one physical variable, which represents a function of the transmission/reception quality of the radio transmitting and receiving device, and which is detected by a detection part and is passed as an input signal to the control device.
The major advantage of the mobile radio transmitting and received device according to the present invention is that the antenna gain is largely stable over a wide frequency range, which is achieved by regulating the variable or variables which represents or represent the reception quality as an optimum value by moving the dielectric body in the near area of the antenna body. In this case, the extent of the overlap of the antenna body and of the dielectric body leaves the polar diagram of the antenna virtually unchanged, thus ensuring good matching over the frequency range. Furthermore, the arrangement has the advantage that the antenna (the antenna body) need not be moved, which is advantageous to the design of the mobile radio transmitting and receiving device, and the external electrical influence is minimized.
A major advantage of one embodiment of the present invention is that any directional electrical influence on the antenna by the user, in particular by his/her head, on the radio transmitting and receiving device is minimized, and vice versa.
Pursuant to another embodiment of the present invention, it is possible to minimize non-directional external influences simultaneously, since they have a greater effect the greater the electrically effective antenna length of an antenna. At the same time, the connection for the radio-frequency signal is applied through the slot which runs parallel to the longitudinal axis, so that the dielectric hollow body can move without impediment and without changing the length of the supply line for the radio-frequency signal.
An advantage of yet another embodiment of the present the invention is the provision of a simple device for adjusting the position of the dielectric body, which requires only one control signal.
Another embodiment of the present invention includes the provision of a simple adjusting part for the position of the dielectric body, which require only one control signal, with the adjustment process being carried out in defined steps (step angles).
Major advantages of another embodiment of the present invention are the flexibility and updating capability for implementation of the control process, which is facilitated by the use of (control) software, and the capability to use already existing processors for controlling the mobile radio transmitting and receiving device according to the present invention by the use of additional software, or by the adaptation of existing software.
In another embodiment of the present invention, advantages are found in the simple and advantageous implementation of the control unit, and the capability to implement this switching mechanism, as an integrated circuit in an expansion module.
An advantage of yet another embodiment lies in the high dielectric constant of ceramic, since the frequency range in which the antenna can be tuned, and thus can be used, increases in proportion to the magnitude of the dielectric constant of the hollow body that is used, and the purchasing costs are low, since ceramic bodies are produced in large numbers; for example, as bodies for resonators.
An advantage of a further embodiment of the present invention is that it is possible to use the mobile radio transmitting and receiving device in a frequency range within which the ratio of the highest to lowest frequency is at least 1.5 octaves.
The detection of the forward transmission power and backward transmission power in another embodiment as a physical variable which represents a function of the transmission/reception quality of the radio transmitting and receiving device allows simple implementation of the control (matching) for the antenna, since parts which already exist in the radio transmitting and receiving device can be used for this purpose.
Additional features and advantages of the present invention are described in, and will be apparent from, the following Detailed Description of the invention and the Figures.